1. Field of the Invention
The present invention relates to a navigation apparatus and a guide route search method suitable to be applied to, for example, a navigation apparatus configured to change a currently shown guide route to a destination.
2. Description of the Related Art
A typical on-vehicle navigation apparatus detects a current location of a vehicle using a dead reckoning sensor or a global positioning system (GPS) receiver, reads map data of the surrounding area from a recording medium, and displays the map data on a screen. A vehicle location mark indicative of the vehicle location is superimposed at a predetermined point on the screen so that the current location of the vehicle can be recognized at a glance.
In most cases, the navigation apparatus includes a route guide function for allowing a driver to easily travel to a desired destination without taking a wrong route. The route guide function includes automatically searching for a route from a current location to the destination with the least cost using the map data, and drawing the searched route on a map screen as a guide route using a different color and a thicker line. The function also includes an intersection guidance of displaying an enlargement of an intersection when the vehicle approaches the intersection to be guided on the guide route within a certain distance, thereby guiding the driver to the destination.
Some navigation apparatuses also include a guide route change function for changing the guide route while guiding the driver to the destination. Such a navigation apparatus can change the currently shown guide route to another guide route to avoid a traffic jam by using the guide route change function when, for example, an accidental traffic jam is caused by an accident, a road construction, a stopped vehicle, or the like ahead of the vehicle while travelling the guide route.
There is disclosed a technology of correcting a part of a route specified before by a user and setting the corrected route as a new route by the user tracing a road on the road map displayed on a display monitor (see, for example, Japanese Patent Application Publication No. 2006-322781).